Conventionally, subscribers tended to limit data usage themselves in order to avoid paying excessive phone bills, but an unlimited data download tariff gives them no incentive to do so. Therefore, a provider of network capabilities needed to support the services offered to subscribers, commonly known as a mobile network operator (MNO), desires a solution by which a high number of subscribers with unlimited data download tariffs, may be offloaded from their network resources (i.e. cellular) onto other networks (e.g. WiFi) and back again, when using certain high bandwidth sessions (e.g. video), and also without having an adverse effect on the subscriber's quality of experience.
In addition, cellular network loads are expected to increase significantly, perhaps as much as three hundred fold over the next 5 years, reaching up to 2 exabytes per month of traffic globally travelling the core network and 23 exabytes annually. This has implications on the operators in terms of power, space and ability to upgrade equipment and cabling, etc. to meet this new demand. This demand will come from the uptake of high bandwidth traffic such as video (TV, user generated video content, wireless video on demand, etc., as well as from logistics applications and other industrial usage, commonly referred to as M2M (Machine to Machine)). Upgrading the mobile operator networks to cope with this challenge will be difficult and so further offload optimisations will be considered.
The difficulty with offloading current and future traffic from the operators network has been that there is not a solution which is easy to implement, works across any operator (worldwide solution), multiple operators, multiple technologies (cellular, wireless local area network, such as WiFi, or Worldwide Interoperability for Microwave Access (WiMAX), etc.), across different equipment manufacturers whilst providing the optimisation directly from the handsets to the offload point (WiFi, WiMAX, etc.), whilst maintaining control in the operators network whilst still managing the quality of service of the signal.
One conventional method by which one network operator has addressed the problem of offloading traffic from the operator's network for mobile phone applications is to use bespoke handsets together with a different Radio Access Network (RAN) piece of equipment called a Generic Access Network/Unlicensed Mobile Access (GAN/UMA). This UMA equipment solves the problem of traffic moving over the mobile operator's radio access part of the network and it also solves the problem of switching between these two types of networks seamlessly. FIGS. 1 and 2 show how this is achieved, where for simplicity it is assumed that the ‘non-cellular’ path always uses a subscriber's home WiFi router.
FIG. 1 illustrates an example using a Universal Mobile Telecommunications System (UMTS) network architecture. When using cellular services, such as UMTS, Global System for Mobile Communications (GSM), code-division multiple access 2000 (CDMA2000), etc., data is sent between a mobile device (UE) 10a, 10b, 10c of FIG. 1 and an internet server 29. In an access network 12 are UMTS base transceiver stations (Node B's) 13, 14 and respective Radio Network Controllers (RNC) 15, 16 by which the UE can communicate with the server 29 via a core network 22 along links Iu-cs 19, 21 or Iu-ps 1b, 20. In the core network 22 are other parts of the mobile operator's equipment including the Gateway GPRS Support Node (GGSN) 24, Serving GPRS Support Node (SGSN) 23. The communication goes over the mobile operator's permitted air interface, through the Access Network cells using the Uu interface 11 from the UE, following the links Iub 1a, Iu-ps 1b, Gn 1c, and link 1d from the NodeB 14 to the IP network 29. The core network 22 also includes mobile switching centre (MSC) 3G-MSC 26 connected to G-MSC 27 via link Nc 30 and thence to public switched telephone network/integrated services digital network (PSTN/ISDN) 28.
When using the subscriber's WiFi router as the air interface, data which is sent to a mobile device from an internet server travels through the operator's core network 22 (GGSN 24 and SGSN 23) and over the Iu-PS interface 1b as in the previous case. However, the GAN/UMA solution sends the data to a GAN Controller (GANC) 31 which transmits the data using a pre-established tunnel to the mobile device 32. This pre-established tunnel travels over the internet to the subscriber's WiFi router and is broadcast over a WiFi connection to the mobile device—this path 2 is shown in FIG. 2 The example illustrated shows a Generic IP Access Network GAN Iu mode functional architecture taken from 3GPP TS43.318.
The mobile device 32 uses the path through the generic IP access network 41 to communicate with the core network 33 via the GANC 31. There is a link Wm between an SGSN 36 of the GANC 31 and an authentication, authorization, and accounting (AAA) proxy server 39 in the core network. There are links Iu-cs to the MSC 37, Iu-ps to the SGSN 38, Iu-pc to SMLC 34 and Iu-bc to the CBC 35. The core network 33 home public land mobile network/visited public land mobile network (HPLMN/VPLMN) also includes a home location register (HLR) 40.
Software in the mobile device 32 registers with the GANC 31, which then controls the path between the operator's core network 33 and the mobile device. The GANC instructs the mobile device to handover between cellular and WiFi. Since the GANC is located in the operator's network, and is treated as an RNC, when a handover occurs data is forwarded between the RNC and GANC to provide a seamless handover.
Whilst this solution provides a seamless session switching solution between two separate access technologies, there are a number of disadvantages. In addition to software on the mobile devices, the operator is required to invest in GANC devices, including the integration of the devices into their own network. Furthermore, only air interface offloading is used, meaning that the data still travels across the operator's core network, which, although still a load to the core network, gives the operator an added benefit of being able to keep each user within their network, with a benefit that they can offer value added services specific to their network users and that the core network (SGSN and GGSN) will still experience capacity problems unless they are upgraded (in which case the cost per bit traversing the core network might be increased). The solution relies on the use of a cellular connection, and cannot be expanded to cover scenarios such as the seamless switching between WiFi hotspots described above.
Current alternatives to using GAN/UMA are for the Mobile Network Operator to do nothing and allow their network to suffer from major capacity problems, or to invest in more cells/higher capacity links and core network equipment to improve the subscriber's experience on their network. The first option is considered to be unwise from a business viewpoint, while the second option is considered to be a high capital expenditure (CAPEX) and operating expenditure (OPEX) investment.
To date, solutions which have been implemented in the handset only provide options to the user to switch the air interface types on, or off. When a secondary air interface (e.g. WiFi) is switched “on”, the mobile device searches, or listens, for a qualified data path to be available, (e.g. WiFi meeting a certain threshold and in range). When the secondary air interface is found and if the device is being used to send/receive data, then the mobile device automatically switches to this secondary interface (e.g. WiFi). This current solution does not allow seamless switching—from cellular to secondary air interface or vice versa, so it cannot start the traffic flow over one set of equipment and finish using a different set of equipment. In order to enable seamless switching, investment needs to be made in a solution such as Mobile IP, but this is also unsatisfactory, as it is not chosen as a global standard Nor do current solutions manage Quality of Service (QoS). Managing mobile quality of service is a requirement in 3GPP and other standard bodies to ensure that the user is provided with different levels of quality for different services. This is an important part of the standards work, as it ensures that the technology being designed can guarantee the users will be able to depend on that technology under many circumstances.
Solutions allowing for seamless bearer transfer between different technologies have been proposed by Attila Technologies, as described in US 2006193295. This solution moves in the direction of a terminal-self-contained traffic offloading technique, where the terminal will use the multi-homing feature supported by the SCTP transport protocol to establish several parallel connections through different radio access technologies and to convey traffic belonging to the same service/bearer across such multitude of connections. In fact, SCTP allows a single data flow to be transported in parallel across different IP routes identified by multiple destination addresses all assigned to the same network node. A terminal supporting SCTP communicating with a server also supporting SCTP can manage such multiple IP routes in a way that they are assigned to different radio access connections. Seamless session mobility between different radio accesses is therefore guaranteed at transport level.
However, this solution relies on the fact that both peers involved in the data exchange support SCTP, which is not always the case. Furthermore, the solution requires a high level of IP address management at the terminal, due to the fact that the primary IP address used by SCTP (the address on which traffic will be preferentially routed) will need to be changed depending on the radio access on which it is most convenient to forward the traffic.